oops.
i created two files in same project.
i thought they are working as two separate files. i just remove first file i created with the codes
#include <iostream>
using namespace std;
int main ()
{
cout << "Hello World! "; // prints Hello
cout << "I'm a C++ program"; // prints I'm a
cin.get();
return 0;
}
so after that the second one executed without errors.